David Brown was an English manufacturer of tractors which was later on taken over by CASE which was then integrated in CNH (Case New Holland). The brand has been discontinued but drawings are still available at the link below.
Find Clasyon parts diagrams ?
To find your David Brown part numbers you can visit the following link.
This link brings you to the CNH parts catalog. You are asked whether you want to sign up, but you can just choose 'No thanks, just launch EPC' and check the legals.